Rare earth based permanent magnet

A rare earth based permanent magnet comprising a sintered compact with an R-T-B based composition, wherein,

• the sintered compact comprises two kinds of main phase grains M1 and M2, wherein, the concentration distribution of R in M1 is different iron that in M2, R comprises R1 and R2, R1 represents at least one rare earth element including Y and excluding Dy, Tb and Ho, R2 represents at least one from the group consisting of Ho, Dy and Tb,
• the main phase grain M1 comprises a core-shell structure which contains a core part and a shell part coating the core part, when the atom, concentrations of R1 and R2 in the core part are defined as αR1 and αR2 respectively, and the atom concentrations of R1 and R2 in the shell part are defined as βR1 and βR2 respectively, the following conditions are met, i.e., αR1>βR1, αR2<βR2, αR1>αR2 and βR1<βR2,
• the main phase grain M2 has a core-shell structure which contains a core part and a shell part coating the core part, when the atom concentrations of R1 and R2 in the core part are defined as γR1 and γR2 respectively, and the atom concentrations of R1 and R2 in the shell part are defined as εR1 and εR2 respectively, the following conditions are met, i.e., γR1 <εR1, γR2>εR2, γR1<γR2 and εR1>εR2, and
• relative to all the main phase grains observed at a unit cross-section of the sintered compact, the ratios occupied by the main phase grains having the core-shell structure are 5% or more, respectively.